Undead Astral Hydra

Undead Astral Hydra enters the battlefield with X +1/+1 counters on it.
{x}{x}{b}{r}{g}, Sacrifice a creature: You may summon Undead Astral Hydra from your graveyard to the battlefield. It has X +1/+1 counters on it.
Even in undeath, the heads really don't really trust each other.